Heretofore, in a store such as a convenience store or a supermarket, there have been installed a plurality of showcases to display and sell articles while cooling the articles in display chambers. An evaporator to cool an interior of the display chamber is disposed in each showcase, and to this evaporator, a refrigerant is supplied from a refrigerator unit installed, for example, outside the store.
Furthermore, in recent years, carbon dioxide has been used as the refrigerant also in this type of showcase, considering from global environmental problems, but a comparatively large type of compressor is required to compress this carbon dioxide. To eliminate such a problem, there has been developed a refrigeration device in which a high stage side refrigerant circuit and a low stage side refrigerant circuit independently constituting refrigerant closed circuits, respectively, are connected in cascade, and a refrigerant of the high stage side refrigerant circuit is evaporated to subcool a high pressure side refrigerant of the low stage side refrigerant circuit, so that a required refrigerating capability can be obtained in an evaporator of the low stage side refrigerant circuit (e.g., see Patent Document 1 and Patent Document 2).